This invention relates to a method for altering the surface of a macroporous cross-linked hydrophobic copolymeric lattice in order to render the lattice hydrophilic. Two mechanisms for accomplishing this surface alteration are provided, along with copolymers produced by both mechanisms. One mechanism relates to the saponification of the surface, whereas the other mechanism involves carboxylation of the surface.
The concept of producing spheres or beads by means of suspension polymerization techniques is well known in the prior art. An exemplary one of such processes is disclosed in U.S. Pat. No. 2,809,943, issued Oct. 15, 1957. However, it was found that when a material was added which is a solvent for the monomers, but acts as a precipitant for the resulting polymer, a novel form of bead was provided containing a network of microscopic channels. This discovery is set forth in U.S. Pat. No. 4,224,415, filed July 18, 1958, issuing some twenty-two years later on Sept. 23, 1980. In this patent, beads are produced ranging in size from about 350 to about 1200 microns. Typical monomers include divinyl toluene, diallyl maleate, and triallyl phosphate. The precipitant employed is said to be an alkane, acid ester, or alcohol.
This technology was expanded and the precipitant was variously described in the patent literature as a diluent, porogen, active ingredient, solvent, functional material, and volatile agent. For example, in U.S. Pat. No. Re. 27,026, issued Jan. 12, 1971, porous beads of a diameter less than ten microns are disclosed. Among the monomers used to produce the beads are ethyl methacrylate, divinyl benzene, and ethylene glycol dimethacrylate. In U.S. Pat. No. 3,418,262, issued Dec. 24, 1968, there is described a bead characterized as having a rigid sponge structure, and wherein the porogenic agent employed is an acid such as stearic acid. Beads ranging in size from 0.5 mm to 500 microns are disclosed. Intermediates in bead form were produced in U.S. Pat. No. 3,509,078, issued Apr. 28, 1970, using polymeric materials such as polyethylene glycols as the precipitant material during the in situ suspension polymerization process. The macroporous character of such bead construction is graphically portrayed and illustrated in FIG. 1 of U.S. Pat. No. 3,627,708, issued Dec. 14, 1971. Beads termed "pearls" are produced, and containing active ingredients therein such as water or various alcohol ethers. The pearls are crosslinked to the extent of about twenty percent. In U.S. Pat. No. 3,637,535, issued Jan. 25, 1972, beads with a sponge structure are said to be capable of being compressed to an imperceptible powder. These beads are capable of being loaded with as much as 200-300% of active ingredients such as white spirit, and benzin. A rigid porous bead of a trifunctional methacrylate is taught in U.S. Pat. No. 3,767,600, issued Oct. 23, 1973. Such beads have a size of 10-900 microns, and various other monomers which can be employed include diacetone acrylamide, and ethylhexyl, hydroxyethyl, and hydroxypropyl methacrylates. Paraffin wax in an amount of 5-100% is used to form the microscopic network of channels in U.S. Pat. No. 3,989,649, issued Nov. 2, 1976. The wax may be removed from the bead structure by solvent extraction.
While many of the foregoing U.S. patents relate to ion exchange technology, a bead similar to those previously described is employed as a carrier for enzymes in U.S. Pat. No. 4,208,309, issued June 17, 1980. Such beads are of the size of about 0.1 mm. U.S. Pat. No. 4,661,327, issued Apr. 28, 1987, describes a macroreticular bead containing a magnetic core. The use of hard crosslinked porous polymeric beads in cosmetics as carriers is taught in U.S. Pat. No. 4,724,240, issued Feb. 9, 1988, wherein various emollients and moisturizers are entrapped therein. These beads are said to be capable of entrapping materials such as 2-ethylhexyl oxystearate, arachidyl propionate, petroleum jelly, mineral oil, lanolin, and various siloxanes. The size of the beads ranges from 1-3,000 microns. Typical monomers include ethylene glycol dimethacrylate, lauryl methacrylate, trimethylol propane trimethacrylate, and dipentaerythritol dimethacrylate. Hydrophobic powders and beads may be produced in accordance with the teaching of this patent. Beads having a rigid sponge structure are also described in U.S. Pat. No. 4,690,825, issued Sept. 1, 1987, and wherein the beads function as a delivery vehicle for a host of materials including pigments, vitamins, fragrances, drugs, repellants, detergents, and sunscreens. The beads have a size of 10-100 microns and are preferably of a monomer system of styrene-divinyl benzene. Crosslinking is said to range from 10-40 percent.
The foreign patent literature includes West German Offenlegungsschrift No. P-2608533.6, published Sept. 30, 1976, and wherein porous polymeric beads produced by suspension polymerization are provided, and which are adapted to release perfumes. A controlled release of the fragrance is disclosed, providing utility for such beads in the home, automobiles, airplanes, railway cars, hospitals, classrooms, conference centers, and gymnasiums. Canadian Pat. No. 1,168,157, issued May 29, 1984, describes hard, discrete, free flowing, bead constructions in which the beads entrap a series of functional materials which can be incorporated into toilet soap, body powder, and antiperspirant sticks. The Canadian Patent, it is noted, is the equivalent of European Pat. No. 61,701, issued on July 16, 1986. In European International Publication No. 0252463A2, published Jan. 13, 1988, there is disclosed a bead having a hydrophobic polymer lattice, and which entraps numerous non-cosmetic materials such as pesticides, pharmaceuticals, pheromones, and various categories of chemicals. Steroids are entrapped, for example, in the porous beads of PCT International Publication No. WO-88/01164, published on Feb. 25, 1988. The steroids are adrenocortical steroids or various anti-inflammatory type steroids. It should therefore be apparent that what began as a simple ion exchange bead concept has rapidly grown into a technology of widely varied application.
In accordance with the present invention, polymer lattices are produced by novel processes not believed to be taught in the prior art, as exemplified by the foregoing patents. Those patents, in general, relate to suspension polymerization processes for the production of porous polymeric and copolymeric spheres and beads in which the precipitant is present during polymerization. These are defined as an "in situ" process. For example, U.S. Pat. No. 4,724,240, while disclosing beads and spheres produced by suspension polymerization techniques in one embodiment, also describes a process involving precipitation polymerization technology, and in which there is produced powder-like materials, in contrast to beads. The PCT International Publication, while a suspension polymerization system, can also be defined as a "post adsorption" process in its use. In this variance, a volatile porogen is polymerized "in situ" and removed by extraction and evaporation, resulting in empty beads. The beads can be loaded with diverse active ingredients, as desired, at subsequent times. Post adsorption techniques are considered to be more attractive because of the flexibility in the selection of active ingredients that can be subsequently entrapped, whereas in the conventional "in situ" suspension systems, the porogen polymerized "in situ" remains in the final product.
What has been accomplished in the present invention, however, is a unique concept differing from all of the foregoing methods, and wherein hydrophilic post adsorbent powders are produced. In contrast to the post adsorbent materials heretofore known in the prior art, hydrophobic powders are treated in order to render the surfaces hydrophilic, thus rendering the powders of the present invention capable of adsorbing liquids having a high surface tension such as formamide, glycerol, and water. The powders of the prior art have traditionally only been capable of adsorbing low surface tension liquids such as hexadecane, dioctylphthalate, bromonaphthalene, ethylene glycol, and methyl iodide. For purposes of the present invention, high surface tension liquids are defined as those liquids having a surface tension generally in excess of about fifty-eight mNm.sup.-1.